My library copy of The Martian by Andy Weir finishes with Mark's rescue by the rest of the Ares 3 crew. The last line is:
This is the happiest day of my life.
However, the LibraryThing page for the book claims that its last line is:
It was a nice, boring afternoon.
Googling this sentence gives me, among other things, a questionably-legal version of the book with an additional scene at the end that's not in my physical copy, in which Mark is on Earth.
Is that scene genuinely part of the book? If so, why is it not in the version I have?